The condition of a battery can be tested with numerous different devices. Such devices determine the charge state or the remaining residual energy, particularly the voltage in the load condition. The required circuit for measuring the voltage under a suitable resistance load and for indicating the measured voltage, even for a rough quantitative indication, is conventional.
Conventional instruments of this type have one or two test leads for contacting the terminals of the battery to be tested. The load condition is then displayed by an indicator. The measurement or test procedure varies depending on the battery type, and specifically on how and where the battery terminals are accessible or can be contacted by the lead or leads.
Battery testers with two test leads are most commonly used. The polarity of the leads is determined by a color code. Improper polarity does not cause damage, but merely requires reversal of the connections between the leads and battery terminals.
Six volt batteries, e.g., those distributed under the name ICE 4 R 25, are very widely used for many purposes, particularly in building site marking lamps. The use in marking lamps is only one of the many large-scale uses of this successful battery type. As a result of widespread use, unskilled persons must be employed to test such batteries economically and determine which batteries requirement replacement. Use of unskilled labor requires simplification of the test procedure to minimize errors. In the case of building site marking lamps, proper testing is necessary to ensure adequate lighting during the hours of darkness for safety and to avoid discarding batteries which are adequately charged.
Conventional testing instruments are not satisfactory for such environments. The instruments are not sufficiently rugged to withstand the rigors of the construction industry. The two-handed operation with test leads is difficult to perform. If the leads are lost, they are merely replaced by any readily available wires tending to cause incorrect measurements. Since such instruments are difficult to use, they are often not used at all and the batteries are not tested, causing complete discharge of the batteries and failure of the lamp. Not infrequently, this creates a considerable safety risk.